Working environment density measuring method

ABSTRACT

An environmental air is sucked by the pump with control unit, and organic solvent contained in the environmental air is collected by the absorbent. Organic solvent having passed through the absorbent is detected by the semiconductor gas sensor. If passage of a material to be measured is detected by the semiconductor gas sensor, operation of the pump with control unit is stopped, and the operation for collecting the material is terminated. Then the absorbent is taken out from the collecting tube, the material collected is quantified by means of gas chromatography, and the density is measured. With this configuration, measurement of a density of a material to be measured in a working environment can be executed accurately.

This application is a Division of application Ser. No. 08/748,980 filedon Nov. 14, 1996, now U.S. Pat. No. 5,861,053.

FIELD OF THE INVENTION

The present invention relates to a solid material collector forcollecting a material to be measured by absorbing thereto the materialas well as to a density measuring method for measuring the densitythereof, and further to a gas mask as well as to an air line mask eachfor improving safety thereof by detecting any of poisonous substanceswhich has passed the solid material collector.

BACKGROUND OF THE INVENTION

As a method of measuring a density of poisonous material such as organicsolvent vapor in a working environment and a dose of a substance towhich a person is exposed in the working environment, there has beenknown a method using an absorbent such as activated carbon, so-called asolid material collecting method. Generally, following effects can beobtained with this solid material collecting method.

(1) Substantially 100% of organic solvent vapor or the like can becollected with an absorbent.

(2) Time-weighted mean of density can be obtained. However with thedirect collecting method, it is possible to measure only a transitionaldensity.

(3) As organic solvent vapor or the like can be condensed, it ispossible to quantify the vapor or the like in a low density. And forthis reason, a range in which the vapor or the like can be measured isvery wide.

(4) A method of gas chromatography (described as "GC" hereinafter) isused for quantifying the vapor or the like, so that even mixed gas ormixed vapor can be measured.

However, an absorbent used for the solid material collecting method hasa limited capacity for absorbing a solid material. For this reason, whenthe collection is executed for a long period of time, poisonoussubstances pass through the absorbent. If any poisonous substances passtherethrough, the measurement will become incorrect.

For this reason, many of commercial solid material collectors have suchconfiguration that adsorbents are packed therein in two layers, in anupstream side as well as in a downstream side of the device. Theabsorbent in the upstream side thereof is used as a sample to beanalyzed by means of the GC. The absorbent in the downstream sidethereof is used for checking whether any of the substances has passedthrough the absorbent or not.

With this configuration, the material to be measured passing through theabsorbent in the upstream side is collected by the absorbent positionedin the downstream side. Accordingly, if any material to be measured isdetected in the absorbent in the downstream side by analyzing it, thefact indicates that the material passed through the absorbent in theupstream side. So, effectiveness of the measurement is determinedaccording to a quantity of the material having passed through theabsorbent in the upstream side. If the quantity is too large, a resultof the measurement is not reliable, which indicates that the measurementis a waste of time.

FIG. 24 shows a partially broken perspective view of a solid materialcollector 900 based on the conventional technology. An absorbent 903 inthe downstream side and that 902 in the upstream side thereof areserially packed in a collecting tube 901. Activated carbon is used forthe absorbents 902 and 903. A duct 904 comes out from an edge section ofthe collecting tube 901. A small size electric pump 905 is connected tothe edge section of this duct 904. The reference numeral 906 indicates aclip for attaching this device to a user. When the pump 905 is driven,environmental air is introduced into the collecting tube 901 through anopening edge thereof. Organic solvent contained in the environmental airis collected by the absorbent 902. The air passing through theadsorbents 902 and 903 passes through the duct 904 to be discharged froman air outlet port of the pump 905.

FIG. 25 is an explanatory view showing how an operator wears the solidmaterial collector 900. The collecting tube 901 is attached with a clip906 onto a shoulder portion of the clothes which a user M wears. Thepump 905 is fixed to a belt or the similar position of the user M. Theuser M works with this solid material collector 900 on. When the work isfinished, the absorbent 902 in the upstream side as well as that 903 inthe downstream side are taken out from the collector. Then, theabsorbent 902 in the upstream side is analyzed with the GC to quantifythe collected material to be measured. The absorbent 903 in thedownstream side is also analyzed. If any material to be measured isdetected from the absorbent 903 in the downstream side, it is understoodthat the material passed through the absorbent 902 in the upstream side.When a quantity of the detected material to be measured is larger than aspecified quantity, a density of the material in the environment or adose of the material to which a person is exposed can not accurately bemeasured. Accordingly, it can be determined that this measurement isinvalid.

However, in the solid material collector 900 described above,effectiveness of the measurement can not be determined before thecollecting work is finished. For this reason, the measurement can notalways accurately be made. And also, the absorbent 902 is sometimeswasted thereby.

There has also been known a method in which a period of time from thebeginning of the measurement until the absorbent 902 is about to bepassed through by the material to be measured under a constant gasdensity is previously measured and the measurement is stopped justbefore passage of the previously determined period of time. However, agas density in the working environment generally changes from time totime and from place to place. Also a user tends to move around in theworking environment. And for this reason, the user can not accuratelyestimate the period of time until a material to be measured startspassing through the absorbent in the upstream side.

It is also conceivable to make a capacity of an absorbent larger.However, when the capacity is made larger, a capacity of a pump isrequired to be made larger proportionately. For this reason, a size ofthe pump becomes large, which lowers portability of the solid materialcollector.

By the way, the absorbent described above is also used for a gas mask oran air line mask used in cases of spraying agricultural chemicals,handling drugs, painting, or cleaning or the like, which is differentfrom the purpose of the absorbent when used for measuring a density ofpoisonous materials in a working environment or a dose of the substancesto which a person is exposed. In these cases, the passage of thepoisonous material through the absorbent becomes an extremely seriousmatter. If the determination that the passage of a poisonous materialthrough the absorbent has been generated is made after it actuallyoccurred, sometimes it is too late.

Currently, there has been employed a method in which a period of workingtime (a period of time before passage of a poisonous material through anabsorbent occurs) is computed from a gas density in the workingenvironment and the work is stopped before the passage actually occurs.However, there is the fear that the period of working time is reducedbecause the gas density in the working environment is not uniform.Especially, in a case where fatally poisonous materials such as chemicalweapons or the like are handled, it may bring about a serious danger toan operator.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a solidmaterial collector which is small in size and can efficiently andaccurately measure a density of of a poisonous material in a workingenvironment or a dose of a material to be measured to which a person isexposed, as well as to provide a density measuring method.

Further, it is a second object of the present invention to provide ahigh safety gas mask as well as a high safety air line mask.

To achieve the object described above, a solid material collectoraccording to the present invention detects passage of a material to bemeasured in a collecting process by a detecting means. With a collectingmeans having a double-layer structure based on the conventionaltechnology, a result of measurement is unreliable in many cases.However, the solid material collector can detect the passage of amaterial to be measured through an absorbent in the collecting step atreal time, which makes it possible to stop the operation for collectingpoisonous materials immediately when the passage is detected. Thereforea result of measurement is reliable. Also, it is possible to performmeasurement even after the passage is generated, so that a result ofmeasurement is quite accurate. In recent years, many detecting meanssuch as a gas sensor and the like have been developed, and use of themeans for solving the problems relating to the passage described aboveis very effective. The detecting means such as a gas sensor is extremelysmall in size, which makes it possible to reduce size of a collector.

A solid material collector according to the present invention detectsthe₋₋ passage before it actually occurs. By providing the detectingmeans at a position adjacent to an edge in the downstream side of thecollecting means, a material to be measured can be detected right beforethe passage is actually generated. Thus, measurement can be executedmore accurately.

A solid material collector according to the present invention maycomprise various types of collecting means, however only especiallyuseful ones are described herein (activated carbon, silica gel, porouspolymer heads, Florisil (a magnesium silicate absorbent), or material tobe measured impregnated therein). For instance, activated carbon has theadvantage that there is no need to cool it down for eliminating watercontent in air and improving the collecting efficiency. When a densityof a material to be collected in the collecting means reaches itssaturation, a material with lower adhesiveness to an absorbent startspassing through the absorbent. On the other hand, if a gas sensor isused as the detecting means, it detects the material to be measurednon-selectively regardless of its type. The object material formeasurement which first passes through activated carbon is detected bythe detecting means. Thus, by stopping an operation for collecting thematerials at a point of time when any material first passes through thecollecting means, passage of other materials each as an object formeasurement can be prevented. As a result, a result of measurement canbe prevented from becoming unreliable. Also, measurement can be executedquite accurately.

A solid material collector according to the present invention of thepresent invention uses a semiconductor gas sensor as the detectingmeans. The semiconductor gas sensor is extremely effective for detectingorganic solvent vapor. It can detect almost all types of organic solventvapor non-selectively, and it has high sensitivity. Also, it is low inprice. Therefore, it is very useful as the detecting means for detectingthe passage of a material to be collected through the collecting means.

The solid material collector according to the present invention asks auser to take any appropriate procedure, because a result of measurementwill become unreliable if the solid material collector continues anoperation for collecting the material to be measured even after thepassage has occurred. The appropriate procedure includes stopping theoperation for collecting the material. An alarming means includes sound,color, light, vibration or the like. As a result, measurement can beexecuted quite accurately and the result is very reliable.

A solid material collector according to the present invention stopsoperations of a sucking means and stops an operation for collecting amaterial to be measured when a quantity of materials having passedthrough the collecting means has exceeded a specified value. With thisconfiguration, effects of the passage will be suppressed to a minimumlevel, and measurement can be executed accurately. Also, a result ofmeasurement is prevented from becoming unreliable. It should be notedthat the specified value described above is set according to sensitivityof the detecting means. For example, it is set according to a result ofan experiment for studying a relation between a result of detection forthe passage by the detecting means and actual state of the passage, orthe like. Details on this matter will be discussed in the section fordetailed description of the preferred embodiments of the presentinvention.

In the solid material collector according to the present invention,sensitivity of the detecting means varies according to a material to bemeasured. Thus, the specified value can be changed freely according tothe material to be measured. Therefore, measurement can be executedaccurately.

The solid material collector according to the present invention recordsa point of time when operation of the sucking means is started, andmeasures an actual period of time when collecting is actually executed.And it quantifies the material to be measured from a flow rate ofenvironmental air during the period of time. With this configuration, itis possible to exclude a period of time when the passage occurred froman actual period of time for measurement, so that measurement can beexecuted accurately. In addition, as a start/stop time recording means,a timer device, which is commercially available, can be used. Therefore,the solid material collector can be provided at low cost.

In the solid material collector according to the present invention, aplurality of the detecting means are provided, and if dispersion isgenerated in output from one detecting means, another detecting means isselected. With this configuration, reliability of output from thedetecting means becomes higher, and measurement can be executedaccurately. In a case where dispersion is generated in all the detectingmeans, it is necessary to replace all the detecting means with new ones.

In a density measuring method according to the present invention, theoperation for collecting the material to be measured is stopped stopswhen passage occurs, and measures density is measured in a state wherethere is no effect of the passage. Thus, measurement can be executedaccurately. Also a result of measurement is reliable. The solid materialcollector described above detects the passage in a step of collecting,so that it is suitable for carrying out the density measuring method.

In a density measuring method according to the present invention, thepassage is detected is detected right before it is actually generated,so that the operation for measurement can be executed in a state whereno passage is generated. To detect the passage right before it isactually generated, the material to be measured is detected at aposition adjacent to an edge section in the downstream side of thecollecting means. With this configuration, measurement can be executedmore accurately.

A gas mask according to the present invention incorporates a detectingmeans at a position adjacent to an edge in the downstream side of thecollecting means. With this configuration, the passage can be detectedright before it is generated. Therefore, the user can take requiredmeasures when the passage is detected. The specified measures includeclosing a shutter so that poisonous gas will not come into a mask bodyand breathing air from an oxygen cylinder, evacuating a working siteimmediately for changing the collecting means to a new one. As a result,higher safety of the gas mask is insured.

A gas mask according to the present invention detects poisonoussubstance having passed through the collecting means in the upstreamside and collects the poisonous substance with the collecting means inthe downstream side. The user can take necessary measures when thepassage is detected. The user will not receive any damage with thepoisonous substance having passed through the collecting means in theupstream side. This insures higher safety of the gas mask. As the userwill stop using the gas mask when the poisonous substance is detected,capacity of the collecting means in the downstream side may be smallerthan that of the collecting means in the upstream side. Therefore, thegas mask can be provided at low cost.

A gas mask according to the present invention detects passage of thepoisonous substance with a detecting means. This configuration issimpler than that of the gas mask described above, which makes its costless expensive. The gas mask with this configuration detects thepoisonous substance which passed through the collecting meanspreviously, so that it is suitable for dealing with substance which iscomparatively less harmful to a human body. But it is not suited to usefor detecting fatally poisonous substances such as chemical weapons.

In a gas mask according to the present invention, various types ofcollecting means can be used. For instance, activated carbon isexcellent for collecting organic solvent. Silica gel is effective forcollecting polarized gaseous materials. Porous polymer beads is suitablefor collecting instable compounds. Florisil is suitable for collectingchlorinated biphenyl (PCB). As for filter paper with a reagentimpregnated therein, filter paper with 2-pyridyl piperazine impregnatedtherein is used for measuring toluene-diisocyanate (TDI); and filterpaper with triethanolamine impregnated therein is used for measuringnitrogen oxide or the like.

A gas mask according to the present invention comprises a semiconductorgas sensor, which is extremely effective for detecting organic solventvapor. The reason is that the semiconductor gas sensor can detect almostall types of organic solvent vapor non-selectively. Therefore, it candetect passage of the poisonous substance without fail. Thus, highersafety of the gas mask is insured.

A gas mask according to the present invention notifies a user for thenecessity to take an appropriate measure for the purpose to prevent thegas mask from being used in a state where any poisonous substance haspassed through the collecting means. The appropriate measures includeimmediate evacuation from the working site. An alarming means includessound, color, light, vibration or the like. As a result, higher safetyof the gas mask is insured.

In the gas mask according to the present invention, a plurality of thedetecting means are provided, and if dispersion is generated in outputfrom one detecting means, the detecting means is switched to anotherone. As a result, higher reliability of the output from the detectingmeans is provided, and also higher safety of the gas mask is insured.

In a gas mask according to the present invention, when the passage isdetected, the fact is notified to a manager or a person other than theuser. Notification is made by radio or the like. Because of thenotification, the person other than the user can realize that the useris in a dangerous situation. In this case, such appropriate measuresshould be taken as giving the user a warning from the manager by radio,rescuing the user immediately when the user is fainted, or the like.

A air line mask according to the present invention incorporates adetecting means at a position adjacent to an edge section in thedownstream side of the collecting means. Thus, it can detect the passageright before the passage is actually generated. The user can takenecessary measures between a point of time when the passage is detectedand a point of time when the passage is actually generated. This insureshigher safety of the air line mask.

In an air line mask according to the present invention, the collectingmeans are provided in the upstream side as well as in the downstreamside, and further a detecting means for detecting poisonous substancesis provided between the collecting means in the downstream side. Thepassage occurs in the collecting means in the upstream side, and thepassage is detected by the detecting means. Also, poisonous substanceshaving passed therethrough is collected in the collecting means in thedownstream side. Therefore, a certain period of time is required from apoint of time when a poisonous material passed through the collectingmeans in the upstream side until a point of time when the materialpassed through the collecting means in the downstream side. As a result,the user can take necessary measures with time allowance even if themask body and the blasting means are located apart from each other. Withthis feature, higher safety of the air line mask is insured.

In an air line mask according to the present invention, the detectingmeans for detecting the poisonous material is provided in the downstreamside from the collecting means. For this reason a user can takenecessary measures after the passage is detected. The necessary measuresinclude replacement of the collecting means and evacuation from theworking site. With this configuration, higher safety of the air linemask is insured. In an air line mask according to the present invention,the mask body and the blasting means are provided apart from each other;so that, in a case where the passage is detected in the side of theblasting means, the user is notified of the fact by radio, wire, or thelike. With this configuration, the user can know and take necessarymeasures. As a result, higher safety of the air line mask is insured.

Other objects and features of this invention will become understood fromthe following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially broken perspective view showing a solid materialcollector according to Embodiment 1 of the present invention;

FIG. 2 is an exploded perspective view showing configuration of a solidmaterial collector shown in FIG. 1;

FIG. 3 is a schematic configuration diagram showing configuration of asolid material collector shown in FIG. 1;

FIG. 4 is a functional block diagram showing functions of a CPU 54 shownin FIG. 3;

FIG. 5 is an explanatory view showing a state where the of a solidmaterial collector shown in FIG. 1 is set;

FIG. 6A is a graph showing a relation between time from a start of anexperiment and density of a material to be measured;

FIG. 6B is a graph showing a relation between time from a start of anexperiment and change rate of the resistance value;

FIG. 7A is a graph showing a relation between time from a start of anexperiment and density of the material to be measured in a case where anobject material for measurement is trichloroethane;

FIG. 7B is a graph showing a relation between time from a start of anexperiment and change rate of resistance value;

FIG. 8 is a flow chart showing a controlling process with the CPU shownin FIG. 3;

FIG. 9 is an exploded perspective view showing Variant 1 of the solidmaterial collector shown in FIG. 1;

FIG. 10 is a partially broken sectional perspective view showing Variant2 of the solid material collector shown in FIG. 1;

FIG. 11 is a perspective view showing a gas mask according to Embodiment2 of the present invention;

FIG. 12A is a view showing general configuration of the gas mask shownin FIG. 11;

FIG. 12B is a view showing general configuration of an externalcontrolling system for controlling a user of the gas mask shown in FIG.11 from outside;

FIG. 13 is a functional block diagram showing a function of the CPUshown in FIGS. 12A and 12B;

FIG. 14 is a flow chart showing a controlling process with a CPU shownin FIGS. 12A and 12B;

FIG. 15 is a view showing general configuration of Variant 1 of the gasmask shown in FIG. 11;

FIG. 16 is a view showing general configuration of Variant 2 of the gasmask shown in FIG. 11;

FIG. 17 is a perspective view showing Variant 3 of the gas mask shown inFIG. 11;

FIG. 18 is a perspective view showing an air line mask according toEmbodiment 3 of the present invention;

FIG. 19 is a view showing general configuration of the air line maskshown in FIG. 18;

FIG. 20 is a functional block diagram showing functions of the CPU shownin FIG. 19;

FIG. 21 is a flow chart showing a controlling process with the CPU shownin FIGS. 12A and 12B;

FIG. 22 is a view showing general configuration of Variant 1 of the gasmask shown in FIG. 18;

FIG. 23 is a view showing general configuration of Variant 2 of the gasmask shown in FIG. 18;

FIG. 24 is a partially broken perspective view showing a solid materialcollector based on the conventional technology; and

FIG. 25 is an explanatory view showing a state where the solid materialcollector shown in FIG. 24 is set.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed description is made hereinafter for the present invention withreference to the related drawings. It should be noted that the presentinvention is not limited by the embodiments described later.

FIG. 1 is a partially broken perspective view showing a solid materialcollector 100 according to Embodiment 1 of the present invention. Anabsorbent 2 for absorbing a material to be measured is inserted in acollecting tube 1. Also sensor sections 3a and 3b are provided in thedownstream side of the collecting tube 1. The reference numeral 4indicates a duct 4. An edge of this duct 4 is connected to the edgesection in the downstream side of the collecting tube 1. On the otherhand, the other edge of the duct 4 is connected to a pump 5 with acontrol unit. The reference numeral 6 indicates a clip with which thecollector is attached onto a user.

The collecting tube is made of Teflon. Commercial activated carbon(produced by Shibata Kagaku) is used for the absorbent 2. The reason isthat the activated carbon described above has an excellent absorbingcapability to an organic solvent. It should be noted that the absorptioncharacteristics of the activated carbon varies according to a type ofcarbon or to conditions for activating the carbon. When the activatedcarbon is used, it is not required to remove moisture in theenvironmental air, nor to cool the absorbent to enhance a collectingrate. This activated carbon is activated when heated and dehydrated in adry air or in a nitrogen airflow under the temperature of around 200° C.

Also this activated carbon has a two-layered structure comprising anA-layer 2a and a B-layer 2b. A quantity of activated carbon required forcollecting a material to be measured must be set taking intoconsiderations a quantity of an object material for measurement to berecovered. For instance, a quantity of the A-layer 2a in this activatedcarbon is 100 mg, and that of the B-layer 2b is 50 mg. It should benoted that the A-layer 2a and the B-layer 2b are fixed to the tube withglass wool 21 and polyurethane foam 22, 23. Actually, these grass wool21, A-layer 2a, polyurethane foam 22, B-layer 2b and polyurethane foam23 are formed to one package to form the absorbent 2. Accordingly,replacement of the absorbent 2 with a new one is executed with a unit ofpackage.

Other than the activated carbon, silica gel, porous polymer beads,Florisil (a magnesium silicate absorbent), or paper with a specificreagent reactive to a material to be measured impregnated therein may beused. Silica gel is effective in collecting a material to be measured ina polarized gas state. Porous polymer beads are suitable for collectingan unstable chemical compound. Florisil (a magnesium silicate absorbent)is suitable for collecting chlorinated biphenyl (PCB) . Also as paperwith a reagent impregnated therein, for instance, paper with2-pyridilpiperazine impregnated therein is used for measurement oftoluene diisocyanate (TDI), and paper with triethanol amine impregnatedtherein is used for measurement of nitrogen oxides.

Materials to be measured include acetone, methyl ethyl ketone, methanol,isopropylalcohol, methyl acetate, ethyl acetate, dichloromethane,chloroform, 1,1,1-trichloroethane, toluene, and normal hexane or thelike. These materials to be measured have weak absorption affinity toactivated carbon, and easily pass through the absorbent.

Provided on the operation surface of the pump 5 with a control unit area display section 55 for displaying passage of a material to be measuredthrough the absorbent or the like, a buzzer 56 for alarming, a powerswitch 58, and various types of function switches 59. The referencenumeral 60 indicates an air outlet port.

FIG. 2 is an exploded perspective view of the solid material collector100 shown in FIG. 1. The collecting tube 1 can be divided into a sensormounting tube 1a for mounting thereonto sensor sections 3a, 3b and aninserting tube 1b for the absorbent 2. The absorbent 2 is inserted intoor taken out of the inserting tube in a state in which the insertingtube 1b has been taken out from the collecting tube. The sensor sections3a, 3b are detachable from the sensor mounting tube 1a. Semiconductorgas sensors 31a, 31b are attached to edge sections of the sensorsections 3a, 3b respectively. These semiconductor gas sensors 31a, 31bare replaceable.

Commercial semiconductor gas sensors developed for monitoring organicsolvent vapor (produced by Ricoh Seiki) are used for the semiconductorgas sensors 31a, 31b. The semiconductor gas sensors 31a, 31b have simpleconfiguration with low price, and non-selectively react to almost alltypes of organic solvent vapor. When a constant current is conducted tothe semiconductor gas sensors 31a, 31b and the heaters are heated up,the resistance value is kept constant in clean air. However, whenorganic solvent vapor is contacted with the surface of the sensor, asemiconductor (n-type oxide such as SnO₂, Fe₂ O₃, ZnO or the like) onthe surface of the sensor is reacted with the organic solvent and theresistance value becomes lower.

Change of a resistance value depends on that of a density as describedlater, so that the density can be determined from the resistance value(a material to be measured can be detected). It should be noted that agas sensor based on the contact combustion system may be used in placeof the semiconductor gas sensor. In this case, a resistance value of thesensor increases according to a reaction of the sensor with the organicsolvent, so that the density can be determined from the increasedportion of the value.

FIG. 3 is a schematic block diagram showing configuration of the solidmaterial collector 100 shown in FIG. 1. The pump 5 with a control unitcomprises a control section 50 and a pump section 51. The controlsection 50 comprises a constant-current circuit 52 for feeding aconstant current to the heaters in the semiconductor gas sensors 31a,31b; an A/D converter 53 for subjecting output from the sensors 3a, 3bto A/D conversion; a CPU 54 for executing specified processing accordingto signals from the A/D converter; a display section 55 for displayingthe fact that the passage of a material to be measured through theabsorbent has occurred; a buzzer 56 for issuing an alarm to a user; anda timer 57 for measuring a period of time from a point of time when thepump section 51 is started to operate until a point of time when thepassage occurs. The pump section 51 sucks a material to be measured withan electric fan, and the sucking force thereof is 0.2 liter/min. Thepump section 51 is also supplied with a power from a small-sizedrechargeable buttery (not shown herein).

FIG. 4 is a functional block diagram showing functions of the CPU 54shown in FIG. 3. The CPU 54 comprises a passage determining section 541for determining that the passage of a material to be measured throughthe absorbent 2 has occurred when resistance values in the semiconductorgas sensors 31a, 31b exceed a specified value described later; aspecified value changing section 542 for changing the specified valueaccording to a type of a material to be measured; an automaticallystopping section 543 for stopping an operation of the pump section 51when the passage determining section 541 determines that the passage hasoccurred; an alarm signal output section 544 for outputting a signal forsounding a buzzer 56 when the passage determining section 541 alsodetermines that the passage has occurred; and an correction timecomputing section 545 for outputting a measurement signal to the displaysection 55.

The CPU 54 also comprises a sensor output monitoring section 546 formonitoring dispersion in output from the semiconductor gas sensor 31a(31b); and a sensor switching section 547 for switching thesemiconductor gas sensor 31a (31b) to the other semiconductor gas sensor31b (31a) when dispersion is generated in the output from the sensor.

FIG. 5 is an explanatory view showing how the solid material collector100 is attached to a user. The collecting tube 1 is attached with a clip6 onto a shoulder portion of the clothes which a user M wears. The pump5 with a control unit is fixed to a belt or the similar position of theuser M. The user M works with this solid material collector 900 on.

Next description is made for a method of setting the specified valuedescribed above. The specified value is previously obtained throughexperiments. FIG. 6A is a graph showing a relation between a period oftime (minutes) from start of the experiment and a density (ppm) of amaterial to be measured. The density thereof was measured by analyzing amaterial to be measured (acetone C33, C37 3/7) passing through theabsorbent 2 with the GC. In this experiment, the passage could berecognized in 37 minutes after start of the experiment. Also in 65minutes after start of the experiment, it was found that the densityexceeded 1300 ppm.

FIG. 6B is a graph showing a relation between a period of time (minutes)from start of the experiment and a change rate in the resistance value(KΩ) of the semiconductor gas sensor 31a (31b). The change rate in theresistance value is obtained by sampling the resistance value of thesemiconductor gas sensor 31a (31b) in relation to elapse of time. Inthis experiment, it was found that the resistance value started tobecome lower in 25 minutes after start of the experiment. Also, in 55minutes after start thereof, the resistance value became constant. Inthis experiment, the resistance value lowered by at maximum 3 KΩ due tothe passage.

As a result, it was found that the semiconductor gas sensor 31a (31b)could detect the passage earlier than the GC. It is also understood thatthe change rate in the resistance value in the semiconductor gas sensor31a (31b) is substantially proportional to that of a density of thematerial to be measured which passes through the absorbent. For thisreason, it is understood that the passage can be detected according to achange rate in a resistance value of the semiconductor gas sensor 31a(31b).

By the way, it is assumed that the specified value is a change rate in aresistance value which does not substantially give any effect over themeasurement of the material to be measured. In Embodiment 1, thespecified value was set to 0.5 kΩ. It should be noted that the densitynot substantially effecting the material, for instance in a case where aspecified allowable density stipulated by law or the like is 750 ppm, isaround +10 ppm. A user inputs this specified value into the collector byoperating various types of function switches 59.

Sensitivity of the semiconductor gas sensor 31a (31b) to the passagevaries according to a material to be measured. For instance, as shown inFIGS. 7A and 7B, in a case where the material to be measured istrichloroethane, a resistance value is changed substantiallyconcurrently when the passage is generated. In this case, unless thespecified value is set to a low value, the passage continues, whichcauses a result of the measurement to be unreliable. The specified valueis changed with the specified value changing section 542.

FIG. 8 is a flow chart showing a procedure of controlling the CPU 54shown in FIG. 3. In step S801, a user turns ON a power switch 58 tostart collection of the material to be measured. In step S802, the pumpsection 51 is started to operate simultaneously when the power switch 58is turned ON. The material to be measured is introduced into thecollecting tube 1 together with the environmental air and collected withthe absorbent 2. The air passing through the absorbent 2 is dischargedthrough the duct 4 from the air outlet port 60.

Control of the CPU 54 is started simultaneously when the power switch 58is turned ON. In step S803, the timer is turned ON simultaneously whenthe measurement is started to start measuring a period of time forcollection. A measurement start signal is transmitted to the collectiontime computing section 545. A period of time for collection is measuredby the collection time computing section 545.

In step S804, a result of detection by the semiconductor gas sensor 31ais sampled. A sampling interval is around 30 seconds. In step S805, aresistance value of the semiconductor gas sensor 31a is computed from aresult of the detection. Subsequently, in step S806, a change rate inthe resistance value is computed from the computed resistance value. Ifthe passage is generated, the resistance value of the semiconductor gassensor 31a is changed as shown in FIGS. 6A and 6B.

In step S807, determination is made as to whether the computed changerate in the resistance value has exceeded a specified value or not. Thedetermination is made by the passage determining section 541. Thespecified value is previously set according to sensitivity of thesemiconductor gas sensor 31a as described above. This specified valuecan also be changed according to types of materials to be measured. Thischange is executed with the specified value changing section 542. If itis determined that the change rate has exceeded the specified value,system control goes to step S808. If it is determined that it has notexceeded the specified value, system control goes to step S811.

In step S808, it is determined that the passage giving substantialeffects to a result of the measurement has occurred, and an alarm isissued. The operation for issuing an alarm is executed by the alarmsignal output section 544. For instance, a display indicating that thepassage has occurred is provided on the display section 55. The buzzer56 is also sounded. In addition to the means described above, vibrationmay be given to a user or a lamp for warning may be lit up. In stepS809, the pump section 51 is automatically stopped by the automaticallystopping section 543. That is because a result of the measurement maybecome unreliable if the operation for collecting the material is stillcontinued even after the passage is generated. In step S810, the timer57 is turned OFF to terminate the measurement of the collecting time.Then a measurement end signal is transmitted to the collection timecomputing section 545.

On the other hand, in step S811, determination is made as to whether thepower switch 58 is OFF or not. If it is determined that the power switch58 is OFF, control of the CPU 54 is terminated. If the power switch 58is still ON, the control of the CPU 54 is continued. In this case,determination is made that the passage giving substantial effects to aresult of the measurement has not been generated because the change ratein the resistance value has not exceeded the specified value. Then thesampling of a result of detection by the semiconductor gas sensor 31a iscontinued until the change rate in the resistance value exceeds thespecified value (steps S802 to S807).

By the way, the sensor output monitoring section 546 always monitorsdispersion in output from the semiconductor gas sensor 31a. Dispersionin output therefrom is generated due to degradation of the semiconductorgas sensor 31a after it has been used for a long period of time. Whenthe sensor output monitoring section 546 detects dispersion in outputfrom the semiconductor gas sensor 31a, the sensor switching section 547switches the semiconductor gas sensor 31a to the semiconductor gassensor 31b.

It should be noted that this switching is executed by interrupting anoutput signal from the semiconductor gas sensor 31a and inputtingthereinto an output signal from the semiconductor gas sensor 31b. Itshould be noted that, when the life of the semiconductor gas sensor 31bis over, the sensor sections 3a and 3b are taken out from the sensormounting tube 1a, and are replaced with new semiconductor gas sensors31a and 31b. The life thereof is displayed on the display section 55.Also, when the life thereof is over during the operation for collection,the buzzer 56 is sounded to let a user know about the fact.

Next description is made for a method of measuring the density. When theoperation for collecting materials to be measured is completed, theinserting tube 1b is taken out from the collecting tube 1 as shown inFIG. 2, and adsorbents 2 are taken out by pushing them out from theinserting tube 1b. Then the materials to be measured collected by eachof adsorbents 2 are separated from each other and quantified accordingto the GC.

Herein, a volume of the environmental air sucked by the pump section 51is computed from the collecting time measured by the collection timecomputing section 545 as well as from the flow rate of the air from thepump section 51. In a case where the control of the pump section 51 tobe automatically stopped is reset and the materials are continued to becollected although the passage has been generated, the quantification isexecuted in consideration of the collecting time measured by thecollection time computing section 545. For instance, if it is determinedthat the passage has continued for 10 minutes, the quantification isexecuted without considering a volume of the environmental air sucked bythe pump section 51 during the period of time.

Next description is made for replacement of adsorbents 2. At first, anabsorbent 2 is pushed into the inserting tube 1b.

Then the inserting tube 1b is mounted onto the sensor mounting tube 1a.It should be noted that, when different materials to be measured arecollected, any absorbent 2 appropriate for the purpose should beselected. A procedure of the replacement is the same as that in a caseof activated carbon.

FIG. 9 shows variant 1 of the solid material collector 100 shown inFIG. 1. The solid material collector 110 is characterized in that thesemiconductor gas sensors 31a and 3 1b are incorporated at positionseach adjacent to an edge in the downstream side of the absorbent 2. Thecollecting tube 111 has a construction in which the tube 111 can bedivided into three sections; a mounting tube 111a for insertingthereinto an absorbent 2, an upstream side fixing tube 111b for fixingthe absorbent 2 from the upstream side of the collecting tube 111, and adownstream side fixing tube 111c for fixing the absorbent 2 from thedownstream side thereof. The absorbent 2 is inserted into and taken outfrom the mounting tube 111a in a state in which the upstream side fixingtube 111b and the downstream side fixing tube 111c have been disengagedfrom the mounting tube 111a.

The sensor sections 3a, 3b are mounted onto the mounting tube 111a. Thesensor sections 3a, 3b are also detachable from the mounting tube 111a.Semiconductor gas sensors 31a, 31b are attached to edges in the sensorsections 3a, 3b respectively. These semiconductor gas sensors 31a, 31bare replaceable.

A duct 4 is attached to an edge of the downstream side fixing tube 111c.This duct 4 is connected to a pump 5 with a small-sized electric controlunit (Refer to FIG. 1, not shown in FIG. 9) . The reference numeral 6indicates a clip for attaching the tube to a user. The configurationother than the sections described above is the same as that in the solidmaterial collector 100.

The solid material collector 110 is assembled as follows. At first, theabsorbent 2 is inserted into the mounting tube 111a. At this point oftime, sensor holes 20 of the absorbent 2 are positioned in the directionof the sensor sections 3a, 3b respectively. Then the sensor sections 3a,3b are mounted to the mounting tube 111a. At this point of time, thesemiconductor gas sensors 31a, 31b are positioned so that the headersections thereof are inserted in the sensor holes 20 respectively. Then,the upstream side fixing tube 111b and the downstream side fixing tube111c are mounted to the mounting tube 111a.

The absorbent 2 is fixed with edge surfaces of screw sections in theupstream side fixing tube 111b and in the downstream side fixing tube111c respectively. The absorbent 2 is replaced with a new one accordingto the same procedure as described above after the collector isdisassembled once. It should be noted that, considering easiness inreplacement of adsorbents, the sensor hole 20 described above may beformed with a key-hole shape. Also, when it is used, this solid materialcollector 110 is attached to a user with the clip 6. The collecting workby the solid material collector 110 is executed in the same manner asthat in a case of the solid material collector 100 described above(Refer to FIG. 8).

With the solid material collector 110 described above, the semiconductorgas sensors 31a, 31b are incorporated at positions each adjacent to anedge in the downstream side of the absorbent 2, so that materials to bemeasured can be detected immediately before the passage is actuallygenerated. As a result of this feature, the measurement can moreaccurately be executed.

A portion of the collecting tube and a sensor section or the like may beintegrated with each other in the pump side. FIG. 10 shows Variant 2 ofthe solid material collector 100 shown in FIG. 1. The reference numeral121 indicates a collecting tube. This collecting tube 121 comprises anintroducing section 121a for attaching the tube onto the shoulderportion of the clothes a user wears, an absorbent fixing section 121cconnected to the introducing section 121a with a duct section 121b, anda collecting section 121d incorporating therein an absorbent 2. Thereference numeral 6 indicates a clip for attaching the tube to the user.

The reference numeral 125 indicates a pump with a small-sized electriccontrol unit. A collecting tube attaching section 1251 for attaching thecollecting tube 121 inside the pump is provided in the upper side ofthis pump 125 with the control unit. A sensor section 123 is provided onthe side face of the pump 125 with the control unit. A semiconductor gassensor 31 is attached to an edge of this sensor section 123. Thissemiconductor gas sensor 31 is replaceable.

Provided on the operation face of the pump 125 with the control unit area display section 1255 for displaying the passage or the like, a buzzer1256 for alarming, a power switch 1258, and various types of functionswitches 1259. The reference numeral 1250 indicates a control section.The reference numeral 1252 indicates an internal tube. The sensorsection 123 is attached to the side section of the internal tube 1252.The edge of the semiconductor gas sensor 31 is projected into theinternal tube 1252 with the sensor section 123 attached thereto. Thereference numeral 1253 indicates a pump section.

The absorbent 2 and semiconductor gas sensor 31 used in Variant 2 arethe same as those used for the solid material collector 100. The solidmaterial collector 120 of Variant 2 has also the same configuration asthat of in the solid material collector 100 (Refer to FIG. 3).

Next description is made for assembling the absorbent 2. At first, theabsorbent 2 is inserted into the collecting section 121d. Then, theabsorbent fixing section 121c is attached to the collecting section 121dfor fixing the absorbent 2 thereto. The sensor section 123 is previouslyattached to the pump 125 with the control unit. The semiconductor gassensor 31 is positioned in the internal tube 1252 with the sensorsection 123 attached to the pump. Then, the collecting tube 121 isattached to the internal tube 1252 by inserting thereinto the collectingtube from the collecting tube attaching section 1251.

The semiconductor gas sensor 31 is positioned in the downstream side ofthe absorbent with the collecting tube 121 having been attached to theinternal tube. The absorbent 2 is replaced with a new one according tothe same procedure as described above after the tube is oncedisassembled. Also when it is used, this solid material collector 120 isattached to a user with the clip 6. The operation for collection by thesolid material collector 120 is executed in the same manner as that in acase of the solid material collector 100 described above (Refer to FIG.8).

With the solid material collector 120 described above, the collector canbe constructed with a compact size. Also, only the introducing section121a is attached to the shoulder portion of the user, so that the usercan work without any load thereon. Also the user does not feel thecollector to be a nuisance.

FIG. 11 is a perspective view showing a gas mask according to Embodiment2 of the present invention. This gas mask 200 is so called a directcoupled type one and comprises a rubber mask body 210 subjected tohalogen-processing for putting on the face of the user, an absorbing can220 for absorbing external poisonous substances, a sensor section 230detachably provided in the absorbing can 220, a control unit 240 forexecuting specified processing according to an output from the sensorsection 230, and an earphone 250 connected to the control unit 240 foralarming the user to the materials.

The absorbing can 220 is possible to be replaced with one according to atype of substance to be absorbed. A absorbent 221 is packed in theabsorbent can 220. Any absorbent 221 appropriate for poisonoussubstances in the working site should be selected. For instance,activated carbon is selected for collecting organic gas. Also, inaddition to activated carbon, silica gel, porous polymer beads,Frolysil, or paper with a specific reagent reactive to a poisonoussubstance impregnated therein may be used.

A poisonous substance includes halogen gas, sour gas, organic gas,carbon monoxide, ammonia, sulfur dioxide, sulfur, hydrocyanic acid,hydrogen sulfide, methyl bromide, and phostkin.

Semiconductor gas sensors 31a, 31b are attached to edge sections ofsensor sections 230a, 230b respectively. These semiconductor gas sensors31a, 31b are the same as those used in Embodiment 1. A gas sensor basedon the contact combustion system may be used in place of thesemiconductor gas sensor.

Provided on the operation face of the control unit 240 are a displaysection 241 for displaying passage or the like, a buzzer 242 foralarming, a power switch 243, and various types of function switches244. An antenna 245 for transmitting the fact that the absorbent ispassed through with the poisonous substances to an external device and aterminal of an earphone 250 or the like are provided on the upper sideof the control unit 240.

FIG. 12A is a schematic block diagram showing configuration of the gasmask 200 shown in FIG. 11. The control unit 240 comprises aconstant-current circuit 246 for feeding a constant current to heatersin the semiconductor gas sensors 31a, 31b; an A/D converter 247 forsubjecting output from the sensor 230a, 230b to A/D conversion; a CPU248 for executing a specified processing according to signals from theA/D converter 247; a communicating section 249 for notifying the stateof passage or the like to an external managing system 280 and receivingsignals from the external managing system 280; and a display section241. The semiconductor gas sensors 31a, 31b are incorporated atpositions each adjacent to inside the mask body in the absorbent 221.The reason is that the passage is detected before it actually occurs.

FIG. 12B is a schematic block diagram showing configuration of theexternal managing system 280 for managing a user with the gas mask 200on from outside. This external managing system 280 comprises acommunicating section 281 capable of communicating with the user withthe gas mask 200 on through the communicating section 249; a controller282 for operating communications; and a microphone 283 as well as a headphone 284 each of which a manager K wears. The reference numeral 285indicates an antenna.

FIG. 13 is a functional block diagram showing functions of the CPU 248shown in FIGS. 12A and 12B. The CPU 248 comprises a passage determiningsection 2481 for determining that the passage is generated in theabsorbent 2 when resistance values of the semiconductor gas sensors 31a,31b each exceed a specified value; a specified value changing section2482 for being capable of changing the specified value according totypes of poisonous substances; an alarm signal output section 2483 foroutputting an alarm signal to an earphone 250 when the passagedetermining section 2481 determines that the passage is generated; and atransmission signal output section 2484 for transmitting a signal, whenthe passage determining section 2481 determines that the passage isgenerated, for the fact to the external managing system 280.

The CPU 248 also comprises a sensor output monitoring section 2485 foralways monitoring dispersion in output from the semiconductor gas sensor31a (31b); and a sensor switching section 2486 for switching thesemiconductor gas sensor 31a (31b) to the other semiconductor gas sensor31b (31a) when dispersion is generated in the output from the sensor.The CPU 248 further comprises a passage recognizing section 4287 fordetermining whether the manager K in the external managing system 280recognizes the fact that the passage has been generated or not.

FIG. 14 is a flow chart showing a procedure of controlling the CPU 248shown in FIGS. 12A and 12B. In step S1401, a user turns ON the powerswitch 243. Controlling of the CPU 248 is started simultaneously whenthe power switch 243 is turned ON, which makes it possible to executecommunications with the external managing system 280.

In step S1402, a result of detection executed by the semiconductor gassensor 31a is sampled. A sampling interval is around 30 seconds. In stepS1403, a resistance value of the semiconductor gas sensor 31a iscomputed from the result of the detection. Then, in step S1404, a changerate in the resistance value is computed from the computed resistancevalue. If the passage is generated, the resistance value of thesemiconductor gas sensor 31a is changed (Refer to FIG. 6).

In step S1405, determination is made as to whether the computed changerate in the resistance value has exceeded a specified value or not. Thisdetermination is made by the passage determining section 2481. Thespecified value is previously set according to the sensitivity of thesemiconductor gas sensor 31a as shown in Embodiment 1. Also, it isdesirable to change this specified value according to any of poisonoussubstances as required. This change is executed by the specified valuechanging section 2482. If it is determined that the change rate hasexceeded the specified value, system control goes to step S1406. If itis determined that the change rate has not exceeded the specified value,system control goes to step S1409.

In step S1406, if it is determined that the passage has been generated,an operation for issuing an alarm is executed. The alarming operation isexecuted according to a signal from the alarm signal output section2483. For instance, the fact that the passage has been generated isdisplayed on the display section 241. A warning beep is given to a userthrough the earphone 250. In addition to the means described above,vibration may be given to the user or a lamp for alarming may be lit up.

In step S1407, the CPU transmits a signal indicating that the passagehas been to the external managing system 280. The transmission signaloutput section 2484 outputs the signal indicating that the passage hasbeen generated from the communicating section 249. This output signal isreceived by the communicating section 281 in the external managingsystem 280. The signal received by the communicating section 281 andindicating that the passage has been generated is transmitted to themanager K. For instance, to whom the passage has been generated isnotified to the manager by means of a warning beep through the headphone 284 or of announcement with an audio signal.

In step S1408, determination is made as to whether the manager K hasrecognized the fact that the passage has been in the gas mask 200 ornot. This determination is made by the passage determining section 2487.More specifically, the manager K operates the controller 282 to transmita signal for recognition from the communicating section 281 in theexternal managing system 280 side. The communicating section 249 in thegas mask side receives this signal. The received signal is sent to thepassage recognizing section 2487 for recognition. On the other hand, ina case where the recognition signal can not be received, thecommunicating section 249 continues to output the signal indicating thatthe passage has been generated to the passage recognizing section untilthe manager K notices it (step S1407, step S1408).

On the other hand, in step S1409, determination is made as to whetherthe power switch 243 is OFF or not. If it is determined that the powerswitch 243 is OFF, control of the CPU 248 is terminated. If it isdetermined that the power switch 243 is still ON, the control of the CPU248 is continued. In this case, determination is made that the passagehas not been generated because the change rate in the resistance valueof the semiconductor gas sensor 31a has not exceeded the specifiedvalue. Then the sampling of a result of detection by the semiconductorgas sensor 31a is continued until the change rate in the resistancevalue exceeds the specified value (steps S1402 to S1405).

When the user does not stop the work even although the passage has beengenerated, the manager K may call the user to stop the work through themicrophone 283. The voice of the manager K is transmitted to the userthrough the earphone 250.

The sensor output monitoring section 2485 always monitors dispersion inoutput from the semiconductor gas sensor 31a. The dispersion in outputtherefrom is generated due to degradation of the semiconductor gassensor 31a after it has been used for a long period of time. When thesensor output monitoring section 2485 detects dispersion in output fromthe semiconductor gas sensor 31a, the sensor switching section 2486switches the semiconductor gas sensor 31a to the semiconductor gassensor 31b.

It should be noted that this switching is executed by interrupting anoutput signal from the semiconductor gas sensor 31a and inputtingthereinto an output signal from the semiconductor gas sensor 31b. At thepoint of time when the life of the semiconductor gas sensor 31b is over,the sensor sections 230a and 230b are taken out from the sensor mountingtube 1a, and are replaced with new semiconductor gas sensors 31a and31b. The life thereof is displayed on the display section 241. Also,when the life thereof is ended while the user is working with it, it isnotified to the user through the earphone 250.

FIG. 15 is a schematic block diagram showing Variant 1 of the gas mask200 shown in FIG. 11. A two-layered absorbent having an absorbent 221ain the upstream side and that 221b in the downstream side is packed inan absorbing can 260. Semiconductor gas sensors 31a, 31b are providedbetween the absorbent 221a and that 221b. Other configuration of variant1 is the same as that in the gas mask 200.

As described above, the mask has a two-layered absorbent 221, and thesemiconductor gas sensors 31a, 31b are provided therebetween, so thatthe passage is generated in the absorbent 221a in the upstream side,which is detected by the semiconductor gas sensors 31a, 31b. After thepassage is detected by the semiconductor gas sensors 31a, 31b, theworking is stopped. Any of the poisonous substances which passes throughthe absorbent is absorbed by the absorbent 221b in the downstream side.For this reason, the user will never absorb any poisonous substanceswhich pass therethrough.

FIG. 16 is a schematic block diagram showing Variant 2 of the gas mask200 shown in FIG. 11. The absorbent 221 is packed in an absorbing can270. Semiconductor gas sensors 31a, 31b are provided in the downstreamside of the absorbent 221. Other configuration of Variant 2 is the sameas that in the gas mask 200.

As described above, provision of the semiconductor gas sensors 31a, 31bin the downstream side of the absorbent 221 makes the configuration ofthe gas mask simpler. Also the manufacturing is made easier, whereby alow price device can be obtained.

A gas mask is not necessarily of a direct coupled type like the gas mask200, and one based on the isolated type may be used. FIG. 17 is aperspective view showing Variant 3 of the gas mask 200 shown in FIG. 11.This gas mask 300 is so-called an isolated type one and comprises arubber mask body 310 subjected to halogen processing for putting on theface of the user, an absorbing can 320 coupled to the mask body 310through a hose 321 for absorbing external poisonous substances, a sensorsection 230 detachably provided in the absorbing can 320, a control unit240 for executing specified processing according to an output from thesensor section 230, and an earphone 250 connected to the control unit240 for alarming the user to the materials.

This absorbing can 320 has a capacity larger than that in the directcoupled type of gas mask 200. The absorbing can 320 can absorb a largerquantity of poisonous substances. And for this reason, the absorbing can320 can be used in adverse working environments. Semiconductor gassensors 31a, 31b are attached to edges of the sensor sections 230a, 230brespectively. These semiconductor gas sensors 31a, 31b are the same asthose in Embodiment 1.

Other configuration of Variant 3 is the same as that in the gas mask200. With this gas mask 300, a user can work more safely even in hostileworking environments.

FIG. 18 is a perspective view showing an air line mask according toEmbodiment 3 of the present invention. This air line mask 400 comprisesa mask body 410 for putting on the face of a user, a communicating unit415 which the user puts on, a communicated pipe 420 coming out from themask body 410, a harness 430 for fixing the communicated pipe 420 to thebody of the user, an air adjusting bag 440 provided at the edge of thecommunicated pipe 420 for adjusting air to be sent, a flow rateadjusting device 450 provided at the edge of the same communicated pipe420 for adjusting air to be sent to an appropriate airflow, and anelectric blower 470 coupled to the flow rate adjusting device 450through the hose 460. In the figure, designated at the reference numeral471 is a power code, at 472 an airflow select switch, and at 473 anantenna.

A power switch 474 and a display section 475 for displaying the state ofpassage or the like are provided on the side face of the housing of theelectric blower 470.

FIG. 19 is a perspective view showing an air line mask 400 shown in FIG.18. A filter 402 and a fan 476 for sending air are provided in thehousing of the electric blower 470. Also, the semiconductor gas sensor31 is incorporated at a position adjacent to the downstream side of thefilter 402. The reason is that the passage can be detected before itactually occurs.

The electric blower 470 comprises a constant current circuit 477 forfeeding a constant current to a heater in the semiconductor gas sensors31, an A/D converter 478 for subject output from the sensor 31 to A/Dconverter, a CPU 479 for executing specified processing according tosignals from the A/D converter 478, a transmitting section 480 fortransmitting the fact that the passage has been generated to thecommunicating unit 415, and a display section 475 for displaying thestate of the passage or the like.

FIG. 20 is a functional block diagram showing functions of the CPU 479shown in FIG. 18. The CPU 479 comprises a passage determining section4791 for determining that the passage has been generated in a filter 402when a resistance value in the semiconductor gas sensors 31 exceeds aspecified value described later, a specified value changing section 4792capable of changing the specified value according to types of poisonoussubstances, and an alarm signal transmitting section 4793 for outputtingan alarm signal to the communicating unit 415 which the user puts onwhen the passage determining section 4791 determines that the passagehas been generated.

FIG. 21 is a flow chart showing a procedure of controlling the CPU 479shown in FIG. 19. In step S2101, a user turns the power switch ON.Control of the CPU 479 is started simultaneously when the switch isturned ON.

In step S2102, a result of detection executed by the semiconductor gassensor 31 is sampled. A sampling interval is around 30 seconds. In stepS2103, a resistance value of the semiconductor gas sensor 31 is computedfrom a result of the detection. Then, in step S2104, a change rate inthe resistance value is computed from the computed resistance value. Ifthe passage is generated, the resistance value of the semiconductor gassensor 31 is changed (Refer to FIG. 6).

In step S2105, determination is made as to whether the computed changerate in the resistance value has exceeded a specified value or not. Thisdetermination is made by the passage determining section 4791. Thespecified value is previously set according to the sensitivity of thesemiconductor gas sensor 31 as shown in Embodiment 1. Also, it isdesirable to change this specified value according to any of poisonoussubstances as required. This change is executed with the specified valuechanging section 4792. If it is determined that the change rate hasexceeded the specified value, system control goes to step S2106. If itis determined that the change rate has not exceeded the specified value,system control goes to step S2107.

In step S2106, when it is determined that the passage has beengenerated, an operation for issuing an alarm is executed. The alarmingoperation is executed according to a signal from the alarm signaltransmitting section 7493. For instance, the fact that the passage hasbeen generated is displayed on the display section 475. The user isnotified that the passage has been generated by means of a warning beepor an audio signal through the communicating unit 415. In addition tothe means described above, vibration may be given to the user or a lampfor alarming may be lit up.

On the other hand, in step S2107, determination is made as to whetherthe power switch 474 is OFF or not. If it is determined that the powerswitch 474 is OFF, control of the CPU 479 is terminated. If it isdetermined that the power switch 474 is still ON, the control of the CPU479 is continued. In this case, determination is made that the passagehas not been generated because the change rate in the resistance valueof the semiconductor gas sensor has not exceeded the specified value.Then the sampling of a result of detection by the semiconductor gassensor 31 is continued until the change rate in the resistance valueexceeds the specified value (steps S2102 to S2105).

FIG. 22 is a schematic block diagram showing variant 1 of the air linemask 400 shown in FIG. 18. An upstream side filter 402a and a downstreamside filter 402b are packed in the housing of the electric blower 470. Asemiconductor gas sensor 31 is provided between the filter 402a and thefilter 402b. A fan 476 for sending air is also provided in the housingof the electric blower 470. Other configuration of Variant 1 is the sameas that in the air line mask 400.

Generation of the passage in the upstream side filter 402a is detectedby the semiconductor gas sensor 31. If the generation is detected, theoperation for issuing an alarm in step S2106 (FIG. 21) is executed. Forinstance, the fact that the passage has been generated is displayed onthe display section 475. The user is notified that the passage has beengenerated by means of a warning beep or an audio signal through thecommunicating unit 415. Any of poisonous substances which passes throughthe upstream filter is absorbed by the downstream filter 402b. For thisreason, the user will never absorb any poisonous substances which passtherethrough. Further, it takes a long period of time for the materialsto pass through the filter 402b in the downstream side, so that the usermay stop working during the period of time and leave the site.

FIG. 23 is a schematic block diagram showing Variant 2 of the air linemask 400 shown in FIG. 18. A filter 402 is packed in the housing of theelectric blower 470. A semiconductor gas sensor 31 is provided in thedownstream side of this filter 402. A fan 476 for sending air is alsoprovided in the housing of the electric blower 470. Other configurationof Variant 2 is the same as that in the air line mask 400.

Generation of the passage in the filter 402 is detected by thesemiconductor gas sensor 31. If the generation is detected, theoperation for issuing an alarm in step S2106 (FIG. 21) is executed. Forinstance, the fact that the passage has been generated is displayed onthe display section 475. The user is notified that the passage has beengenerated by means of a warning beep or an audio signal through thecommunicating unit 415. Then the user stops working and leaves siteafter the fact is notified.

As described above, provision of the semiconductor gas sensor 31 in thedownstream side form the filter 402 makes the configuration of the airline mask simpler. Also the manufacturing is made easier, whereby a lowprice device can be obtained.

As explained above, the solid material collector according to thepresent invention can determine with by a detecting means whetherpassage of a material to be measured through an absorbent has actuallybeen generated or not in the step of collecting the material at realtime. For this reason, a result of measurement is prevented frombecoming unreliable. Also, it is possible to prevent measurement frombeing continued in a state where the passage has been generated, so thatmeasurement can be executed accurately. Size of the solid materialcollector can be reduced because the detecting means is small in sizeand there is no need to increase an quantity of adsorbent used therein.

The solid material collector according to the present inventioncomprises a detecting means incorporated at a position adjacent to anedge in the downstream side of a collecting means; so that it can detectthe material to be measured right before the passage is actuallygenerated. Therefore, the passage can be prevented before it actuallyoccurs, and measurement can be executed more accurately.

The solid material collector according to the present invention usesactivated carbon, silica gel, porous polymer beads, Florysil, or filterpaper with a specific reagent reactive to a material to be measuredimpregnated therein, as the collecting means. Therefore, the operationfor collecting can be executed appropriately.

The solid material collector according to the present invention uses asemiconductor gas sensor as the detecting means. The semiconductor gassensor can detect almost all types of organic solvent vapornon-selectively, and it has high sensitivity . Thus, it can detect thepassage precisely. The semiconductor gas sensor itself is relativelyless expensive, whereby the solid material collector can be provided atlow cost.

The solid material collector according to the present invention notifiesa user, when said detecting means detects the material to be measured,of the fact. Therefore, by taking necessary measures such as stoppingthe operation for collecting, measurement can be executed efficientlyand accurately and a reliable result can be obtained.

The solid material collector according to the present inventionautomatically stops the operation of the sucking means when an outputfrom said detecting means exceeds a specified value. Thus, effects ofthe passage can be suppressed to a minimum level, and measurement can beexecuted accurately. Also, a reliable result of measurement can beobtained.

In the solid material collector according to the present invention, itis possible to change the specified value according to a material to bemeasured. For this reason, the solid material collector canappropriately respond to various types of materials to be measured, andexecute the operation for measurement accurately.

The solid material collector according to the present invention recordsa point of time when operation of a sucking means is started, andmeasures actual time when operation for collecting is actually executed.Measurement can be executed without being bothered by considerations toa period of time where the passage is actually generated.

The solid material collector according to present invention comprises aplurality of said detecting means and selects other detecting means whendispersion is generated in output from one detecting means. For thisreason, reliability of the output from the detecting means becomeshigher, and measurement can be executed accurately.

A density measuring method according to the present invention stops theoperation for collecting when the passage is detected and measures adensity of a material to be measured in a state where there is no effectof the passage. For this reason, accurate measurement can be executed.

The density measuring method according to the present invention detectsthe passage right before it is generated, and executes the operation formeasuring in a state where the passage has not been generated. For thisreason, the operation for collecting can be executed most effectivelyand further measurement can be executed more accurately.

The gas mask according to the present invention detects the passagegenerated in the gas mask by a detecting means incorporated at aposition adjacent to an edge section in the downstream side of acollecting means. For this reason, the passage can be detected before itis actually generated, which insures higher safety of the gas mask.

The gas mask according to the present invention comprises two layers ofcollecting means, detects poisonous substance having passed through thecollecting means in the upstream side, and collects the poisonoussubstance with the collecting means in the downstream side. Therefore,even though the passage is generated in the collecting means in theupstream side, a user will not receive any damage with the poisonoussubstance. This insures higher safety of the gas mask.

The gas mask according to the present invention provides the detectingmeans in the downstream side from the collecting means and detects thepoisonous substance coming into a mask body. This configuration issimpler than that of the gas mask described above, which makes the costless expensive. Also safety of the gas mask is insured.

In the gas mask according to the present invention, the collecting meansis activated carbon, silica gel, porous polymer beads, Florysil, orfilter paper with a specific reagent reactive to the material to bemeasured impregnated therein. Therefore, an operation for collectingpoisonous materials can be executed appropriately.

The gas mask according to the present invention uses a semiconductor gassensor as the detecting means. The semiconductor gas sensor can detectalmost all types of organic solvent vapor non-selectively, and it hashigh sensitivity. Therefore, it can detect passage of the poisonoussubstance accurately, which insures higher safety of the gas mask.

The gas mask according to the present invention comprises an alarmingmeans for notifying a user, when said detecting means detects anypoisonous substance, of the fact, and instructs the user to takenecessary measures. For this reason, higher safety of the gas mask isinsured.

The gas mask according to the present invention comprises a plurality ofsaid detecting means and selects other detecting means when dispersionis generated in output from one detecting means. With thisconfiguration, reliability of the output from the detecting means isobtained, and higher safety of the gas mask is insured.

The gas mask according to the present invention comprises a notifyingmeans for notifying a manager or a person other than the user, when saiddetecting means detects any poisonous substance, of the fact. Therefore,measures for safety and rescue can be taken.

In an air line mask according to the present invention, the detectingmeans for detecting a poisonous substance is incorporated at a positionadjacent to an edge section in the downstream side of the collectingmeans, which is provided between the blasting means and said mask body.For this reason, it can detect the passage right before the passage isactually generated, so that higher safety of the air line mask isinsured.

The air line mask according to the present invention comprises twolayers of collecting means, and also a detecting means for detecting thepoisonous substance between the collecting means. The detecting meansdetects poisonous substance having passed through the collecting meansin the upstream side. And the poisonous substance having passed throughthe collecting means is collected by the collecting means in thedownstream side. For this reason, higher safety of the air line mask isinsured.

The air line mask according to the present invention comprises adetecting means for detecting the poisonous substance provided in thedownstream side from the collecting means. For this reason, highersafety of the air line mask is insured. The configuration of this airline mask is simpler than that of the air line mask described above,which makes its cost less expensive.

The air line mask according to the present invention notifies the user,when the detecting means detects any poisonous substance, of the fact.For this reason, the user is notified of generation of the passage evenif the passage occurs at a position away from the user. This insureshigher safety of the air line mask.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

What is claimed is:
 1. A density measuring method for measuring adensity of a material collected in a working environment by a collectingunit configured to collect the material to be measured, said methodcomprising:receiving and collecting the material from the workingenvironment in the collecting unit at an upstream side of the collectingunit; providing a detector configured to detect the material at adownstream side of the collecting unit, said downstream side being aside opposite to the upstream side; detecting passage of the materialthrough said collecting unit by said detector; stopping the step ofreceiving and collecting the material when said passage is detected; andmeasuring the density of said material by quantifying the material beingcollected in said collecting unit until the step of stopping thereceiving and collecting of the material.
 2. A density measuring methodfor measuring a density of a material collected in a workingenvironment, said method comprising:collecting the material in acollecting unit; detecting the passage of the material through thecollecting unit at a position adjacent to a downstream side of saidcollecting unit, said downstream side being opposite to a side of thecollecting unit initially receiving the material being collected;stopping the step of collecting the material when said material isdetected in said detecting step; and measuring a density of the materialby quantifying the material collected by said collecting unit until thestep of stopping the collecting of the material occurs.